结渣是限制高碱煤大规模燃烧利用的关键问题,针对该问题以高碱金属和高碱土金属两类电站锅炉灰渣为研究对象,通过灰熔融温度测试仪、热机械分析仪、热重-示差扫描量热仪、XRD以及热力学软件FactSage系统探究了高碱煤灰渣结渣倾向及结渣过程。研究发现高碱煤灰渣中碱金属主要以硅铝酸盐存在,而碱土金属主要以硫酸盐存在。高碱金属煤灰渣初始烧结温度高于高碱土金属灰渣,但高碱土金属煤灰渣熔融温度范围大于高碱金属煤灰渣。初始烧结温度与沉积指数均可用于高碱煤灰渣结渣倾向判断,但灰渣化学成分中CaO、K2O+Na2O、SiO2/Al2O3、碱酸比B/A及矿物成分中碱土金属硫酸钙、碱金属硅铝酸盐含量与结渣倾向判别指数间无直接对应关系。高碱煤灰渣的熔融主要经历2个阶段,第1阶段是低熔点碱金属矿物(钠长石、霞石)的熔融或与煤灰中其他矿物反应(石英、白榴石)形成初始液相;第2阶段主要是碱土金属矿物(辉石、钙长石)参与低温共熔反应形成大量液相。

Slagging is a serious problem limiting the large - scale combustion and utilization of coal ashes with high alkali. Two typesof combustion boiler slags with a high alkali metal and high alkaline earth metals respectively were used to investigate the slagging tenden⁃cy and slagging process by ash fusion temperature tester, thermomechanical analyzer, thermogravimetric-differential scanning calorimeter,XRD, and thermodynamic software FactSage. It is found that the alkali metal in the high alkali ash slag mainly exists in silicoaluminate,while the alkaline earth metal mainly exists in sulfate. The initial sintering temperature of high alkali coal ash slags (SH and PG) is higherthan the coal ash slags with high alkaline elements (GJ and CQ), but the ash fusion temperature range of GJ and CQ is larger than SHand PG. Both initial sintering temperature and deposition index can be used to evaluate the slagging tendency of coal ashes with high basicoxides, but there is no direct relationship between the slagging tendency discrimination index and the chemical composition of the ashCaO, K2O+Na2O, SiO2 / Al2O3, alkali acid ratio B/ A, and the content of alkaline earth metal calcium sulfate and alkaline metal silicateAluminate in the mineral composition. The melting of coal ashes with high basic oxides mainly passed through two stages. The first stageis connected to the melting of low-melting-point alkali metal minerals (albite, nepheline) or the reaction with other minerals in coal ash(quartz, albite) to form the initial liquid phase, the second stage is mainly dominated by low-temperature eutectics which are formed bypyroxene and feldspar.

0 引言

1 试验

   1.1 样品制备及表征

   1.2 灰熔融过程收缩特性测试

   1.3 灰熔融温度测试

   1.4 TG-DSC测试

   1.5 物相分析

   1.6 热力学计算

2 结果与讨论

   2.1 高碱煤灰渣结渣倾向

   2.2 灰渣化学/矿物组成对高碱煤灰渣结渣倾向的影响

   2.3 不同高碱煤灰熔融过程

3 结论